1. Field of the Invention
This invention relates to devices which prevent shock caused by collision after rapid coaxial movement or collapse of telescoping members of a support structure, particularly to devices which do not function solely on a pneumatic principle.
2. Description of the Prior Art
Several methods, have been advanced to regulate the relative movement of collapsing telescopic structures. Earlier devices generally often employed a spring loaded or friction latch device to prevent the tubes from collapsing under load. More recent devices may incorporate pneumatic principles, as in automobile shock absorbers, or door closing devices.
Important considerations in the design of shock absorbing devices or snubbers to reduce shock to fragile objects being supported on telescoping structures are capacity to absorb shock, weight, smoothness of operation, safety and effect on appearance. Other prevailing considerations are cost of manufacturing, and, especially in the case of support devices for the medical patient care, such as intravenous fluid bag support stands, reliability. The latter consideration is facilitated in designs that incorporate fewer component parts.
Shock absorbing contrivances of various designs are available commercially, but none have all of the desireable features stated above.
U.S. Pat. No. 2,664,259, issued to Rose describes a hanger which utilizes both frictional and pneumatic forces for vertical adjustment of an object mounted under a suspended telescoping support. The position of the object is adjusted and maintained by an exterior friction clamp comprised of a base plate, containing an aperture through which a coaxial rod passes, affixed to the outer tube, and another plate with a slightly larger aperture, which is spring-loaded on an obtuse angle to the first plate. While releasing the clamp to adjust position, the suspended article may be lowered at a speed controlled by a pneumatic device comprising a leather cup such as is found in a tire pump mechanism.
U.S. Pat. No. 1,447,519, issued to Schade, describes a friction clutch for telescoping elements. The several embodiments described can be activated by various remote means, while the effective gripping part is carried by the inner telescopic element and is movable to project outwardly to operate against the inner circumference of the outer telescopic element. Friction is the only operative force used.
A very complex, linearly adjustable device fixable by a locking mechanism is described by Lampert in U.S. Pat. No. 3,506,287. This device utilizes friction forces alone.
It is therefore desirable to have a device which overcomes the deficiencies of prior art apparatus in a device that is simple, reliable and effective.